package com.example.week9_advanceui;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by 92066 on 2022/4/25.
 */

public class StudentDBHelper extends SQLiteOpenHelper {
    //数据库名称
    private static final String DB_NAME = "students.db";
    //表名
    private static final String TBL_NAME = "student";
    //声明 SQLiteDatabase 对象
    private SQLiteDatabase stuDB;
    //构造方法
    public StudentDBHelper(Context context) {
        super(context, DB_NAME, null, 1);
    }
    @Override
    public void onCreate(SQLiteDatabase database) {
//获取 SQLiteDatabase 对象
        this.stuDB = database;
//创建表
        String CREATE_TBL = "CREATE TABLE student(_id integer primary key autoincrement, num text, name text)";
        stuDB.execSQL(CREATE_TBL);
    }
    //插入一行
//参数：values - 要插入的 ContentValues 对象
    public void insert(ContentValues values) {
        SQLiteDatabase db = getWritableDatabase();
        db.insert(TBL_NAME, null, values);
        db.close();
    }
    //查询（获得全部）
    public Cursor query() {
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.query(TBL_NAME, null,
                null, null,
                null, null, null);
        return cursor;
    }
    //删除一行
//参数：id - 要删除记录的_id
    public void del(int id) {
        if (stuDB == null)
            stuDB = getWritableDatabase();
        stuDB.delete(TBL_NAME, "_id=?", new String[]{String.valueOf(id)});
    }
    //关闭数据库
    public void close() {
        if (stuDB != null)
            stuDB.close();
    }
    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
    }
}

